1. Field of the Invention
The present invention relates to a digital color copying machine, and more particularly, to a digital color copying machine capable of performing a test mode for making a color adjustment.
2. Description of the Related Art
A conventional digital color copying machine comprises a reading section for reading an image of a document by using a color image sensor and converting the image of the document into image data for printing, and an electrophotographic printer section for printing an image of the document on copying paper according to the image data. In the case that plural color images are to be superimposed on a copying paper, the document is read out repeatedly by the reading section, and each color image is printed on the same copying paper by the printer section in the order of respective colors predetermined.
The reading section comprises a masking circuit for generating a color-corrected signal corresponding to printing characteristics of the printer section. Generally speaking, it is difficult for the masking process circuit to minimize the color difference between the real document and the copy thereof with respect to all the colors contained therein. Therefore, in such a case that a copy is further copied as a document, the color tone of the secondary copy may be considerably different from that of the original document. However, in the range of a limited color tone, if a better color balance adjustment is performed, the variation of the color tone can be minimized.
Conventionally, the color balance adjustment is performed by referring to a copy obtained in a certain color balance in a manner of so-called cut and try. In this case, the scanning operation of the document is repeated by a number of times which is a product of a number of times of the color balance operation needed for obtaining a desired color copy and a number of the printing colors, and therefore, the color balance operation is time consuming and laborious.
Generally, in the conventional digital color copying machine, in order to adjust a color balance upon making a color adjustment, for example, there are set respective color adjustment coefficients of cyan color, magenta color and yellow color. Namely, the above color adjustment coefficients are normally set at predetermined standard levels, respectively, and when a color balance of an image to be printed on a copying paper is altered, respective color adjustment coefficients are set at proper levels, respectively.
The inventors of the present invention have proposed a color adjustment selecting method (referred to as a mosaic monitor method hereinafter) for decreasing the time and cost required for the color correction in the U.S. patent application Ser. No. 321,405 as filed on Mar. 10, 1989. In this mosaic monitor method, a part of a document (referred to as a specific area hereinafter) including a partial image for example, a face of a person, for which the operator desires accurate the color reproduction, is set by a specific area setting means. Then, image data of the specific area is stored in an image memory means. Next, the color adjustment is made for the image data read out from the image memory means with predetermined various color adjustment coefficients, and then image data having different color balance are printed at different positions of the same copying paper in a mosaic-like pattern. Thereafter, the operator selects an image having a color balance nearest to that of a document or an image having a color balance most desirable for the operator among plural images of the specific area (referred to as mosaic monitor images hereinafter) which have been reproduced with different color balances, respectively. Thereafter, a copy of the whole area of document is produced based on the color adjustment coefficients of the mosaic monitor image selected. Thus, a copy of document having the most desirable color balance can be obtained easily.
In this digital color copying machine using the mosaic monitor method, different plural levels of each of the color adjustment coefficients y.sub.i, m.sub.i and c.sub.i (i=1, 2, 3, . . . ) are set previously, and the color adjustment is made for an image of a partial specific area repeatedly under the condition of plural color balances which have different combinations (y.sub.i, m.sub.j and c.sub.k) of respective set color adjustment coefficients each other, respectively. Thereafter, the mosaic monitor images comprised of plural test images having different plural color balances each other is printed on a copying paper, and the operator selects an image having the most desirable color balance among the mosaic monitor images. Thus, it becomes easy for the operator to select an image having the most desirable color balance.
However, conventionally, the operator is not informed of respective color adjustment coefficients of the selected color balance.
If respective color adjustment coefficients of the selected color balance are informed brought to the operator's attention it becomes easier to select an image having a preferable color balance among the mosaic monitor images. For example, in the case that the operator wishes to reproduce a document image with substantially complete fidelity, or in the case that the operator wishes to make a minute color adjustment under the condition of a middle level between selectable adjustment levels of each of the color adjustment coefficients, information regarding the color adjustment coefficients becomes helpful to the operator in selecting respective color adjustment coefficients. Further, in the case that plural mosaic monitor images having various sorts of color balances respectively are printed on copying papers in order to search for a desirable color balance, the information of the color adjustment coefficients becomes helpful to the operator in selecting respective color adjustment coefficients on the next trial. Furthermore, even in the case that a proper color balance has been searched among the mosaic monitor images. If respective color adjustment coefficients of the searched color balance are brought to the operator's attention, it is expected that a color balance can be selected more properly by such an experience.